From: Sarah Van Keuren (svk@steuber.com)
Date: 03/29/01-10:01:55 PM Z
> With gum printing, I'm building layers of
> exposures on top of each other. A flat ammonium dichromate exposure will
> complement a more contrasty potassium dichromate exposure (in certain
> situations). So, given the multiple printing aspect and tremendous
> flexibility of the gum process, I've never found the need for a super
> precise speed/contrast control when making individual exposures. One of the
> beauties of gum is that if your first exposure is too weak/strong or
> flat/contrasty you can always compensate with subsequent exposures.
>
> Contrast can also be altered in gum printing by manipulating the gum&pigment
> to sensitizer ratio. My normal ratio is 1:1. If I mix 2 parts gum&pigment
> to 1 part sensitizer the contrast will be increased. Or if I mix 1 part
> gum&pigment to 2 parts sensitizer, the result is lower contrast.
>
> The manipulation and control possible with gum is a fascinating topic. I
> could go on and on, but I'll stop here.
>
> Dave Rose
Dave, what you wrote above is exactly my experience. Like a painter
responding to an area of brushwork with another area of brushwork, a gum
printer reacts to one layer with another layer, balancing, compensating,
emphasizing, deemphasizing. And what you wrote about control through
manipulating the gum/pigment ratio is what I discovered empirically also. It
is such a plastic medium in the old sense of the word.
Sarah
P.S. Speaking of plastic in the newer sense and thinking of the talk in
subsequent List emails, especially from Sandy King comparing carbon printing
to gum printing, I have always thought that polymer plates that printmakers
use for both relief and intaglio printing (using light resists and actinic
light) utilized dichromate in an unhardened plastic colloid. I see that
chromium orange glinting within the thick polymer layer. I heard that
polymer plates were first thought of in the U.S. but that there were
technical problems. The Japanese bought the patent or the company and solved
the technical problems. Nobody knows or even seems to wonder just how they
work but the word is that they are non-toxic. Does anyone on the List have
the scoop on polymer plates?
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